|
Dan,
Actually, an active thruster will make you turn quicker than a rudder--and that's the problem. For transects, where you have to get from point A to point B, and need to do it quickly, then the rudder foil DAMPENS the quick steering. This makes it lazier, so to speak, and easier to correct. The big rudder ticks back and forth, too, but doesn't have to work too hard, and doesn't snap the boat around on you when you bend down for two seconds to scratch your ankle (or your girl friend's ankle, come to that).
Of course, you pay for it in close maneuvering, where the rudder is less efficient. You can turn a Perry boat on its nose by putting the rudder all the way over and goosing that big wheel HARD and, like I said, they work very well at cruising speeds, like running pipeline or cable inspections. Rudders are a whole lot more efficient than lateral thrusters if you factor wattage into the picture. We worked all day in the things, day after day, and anything you could do to conserve power was worth doing. Rudders take less juice, and that was important at the time.
However, mid-water maneuvering near the rigs or whatever needed all the thrusters you had, and made you wish for a couple of more. That's where the JSLs excel. All those thrusters can turn the sub any way but inside out, and as long as you don't need to get anywhere in a hurry, then whoppee, is it fun!
On the opposite side of the spectrum, the Aquarius (for instance) had a single 5hp unit aft, one of the standard Hyco Hymak thrusters, and no rudder. We chased it back and forth hydraulically for steering, which is less stressful than George's rudder yoke, to be sure. You'll note that Phil dumped that unit entirely and replaced it with the system off his Deepworkers. Aquarius was my favorite little-bitty sub (the hull is 4 X 9 feet, sub is 13 and a little bit), but was a pain in the butt to operate due to its lack of vertical maneuvering ability. Phil has fixed that, and boy do I wish that I could take a crack at it today. I'll bet it's dandy.
The Hyco boys never did like rudders, and didn't use them. All the Pisces subs used twin side-mounted thrusters, and you couldn't drive them in a straight line in mid-water except below a walking pace (believe me, I've tried!). They were famous for wandering. I remember a job Hyco did that required long mid-water transects and they built fins, big, inverted kind of negative Beaver looking things, to help stabilize the boat. It apparently worked well enough to get the contract done.
Maybe a fin like the one George used would help dampen the wandering on yours. I just don't know. Can you put something on temporarily, just to test it? George's fin was foil shaped and pretty narrow. Maybe something bigger? Your guess is as good as mine. Maybe cook up some kind of test rig mounted from the aft lift lug to the towing ring behind the MBT and cut several fins (look at the old Nektons to see what I'm thinking about).
The JSLs use multiple thrusters to work around all this, but they are nearly the size of a city bus these days, and react to inputs in a leisurely fashion. Of course, they weigh 14-tons, too, and that's a lot of mass to shove around. Mind you, considering the size of my waistline these days, shoving mass around is going to be an important consideration. At least for me.
Vance
|